Catheters and catheter-like devices have been used for many years in the diagnosis or treatment of various disorders or conditions within the human body. It is become commonplace, for example, to introduce catheters through the vascular system of patient in order to diagnose or treat conditions within the human heart.
One example of a catheter for treating body tissue is described in U.S. Pat. No. 4,860,744. The medical catheter described therein is used in treating internal tumors or other growths located on the internal body tissue of a patient. The catheter is inserted into the patient's body and is advanced to the area to be treated. X-rays allow the physician to monitor the progress of the catheter through the patient's body. Once the tip of the catheter reaches the area of tissue to be treated, the catheter tip is heated and applied to the tumor so as to eliminate it.
Another catheter and catheterization method are described in U.S. Pat. No. 5,147,355. The catheter in that patent is also guided through a patient's blood vessels to a location within the patient's body, such as the area of the heart, so that the tip of the catheter is adjacent to the area of tissue to be treated. Once in place, the tip of the catheter is cryogenically cooled and applied to the selected area of tissue. Applying the super-cold tip of the catheter ablates the area of tissue.
A catheter for treating disorders associated with the conduction of electrical signals in cardiac tissue is described in U.S. Pat. No. 4,641,649. The catheter described therein includes an antenna located at the distal tip of the catheter. The antenna receives electrical signals from the heart and transmits them to a recording device, thus purportedly allowing the physician to determine the source of the cardiac disorder. Once the source has been located, radio frequency or microwave frequency electrical energy is applied to the section of tissue through the tip of the catheter to eliminate the source of the electrical disorder.
Although the use of catheters for diagnosing and treating medical conditions has been long accepted, one pervasive problem is in anchoring and retaining the catheter tip at the desired section of body tissue. This problem is most common when treating organs that are subjected to repeated movements such as the heart. As described in detail below, the continuous movement of the heart muscle and pulsating flow of blood therethrough often makes it difficult for a physician to position and retain the catheter tip at a selected site within the heart long enough to perform the desired treatment procedure (e.g. ablation) or diagnosis.
The human heart has four chambers for receiving blood and for pumping it to various parts of the body. In particular, the two upper chambers of the heart are called atriums, and the two lower chambers are called ventricles.
During normal operation of the heart, oxygen-poor blood returning from the upper and lower extremities of the body enters the upper right chamber known as the right atrium. The right atrium fills with blood and eventually contracts to expel the blood through the tricuspid valve to the lower right chamber known as the right ventricle. As the right atrium relaxes, blood fills the right ventricle. Contraction of the right ventricle ejects the blood in a pulse-like manner from the right ventricle to the pulmonary artery which divides into two branches, one going to each lung. As the oxygen-poor blood travels through the lungs, it becomes oxygenated (i.e. oxygen-rich).
The oxygenated blood leaves the lungs through the pulmonary veins and fills the upper left chamber of the heart known as the left atrium. When the left atrium contracts, it sends the blood through the mitral valve to the lower left chamber called the left ventricle. Contraction of the left ventricle, which is the stronger of the two lower chambers, forces blood through the main artery of the vascular system known as the aorta. The aorta branches into many smaller arteries and blood vessels that eventually deliver the oxygen-rich blood to the rest of the body.
Typically, diagnosis or treatment of cardiac disorders, such as cardiac arrythmia, requires introducing a catheter into the heart as disclosed, for example, in U.S. Pat. Nos. 5,147,305 and 4,641,649. However, as described above, the constant contraction and relaxation of the heart muscle, together with the pulsating flow of blood therethrough, makes accurate placement of catheter difficult even in the best of circumstances.
Because of the difficulty in accurately positioning and retaining the tip of the catheter tip at the desired location in a pumping heart, there exists today a need for suitable methods and/or apparatus that will allow the physician to anchor and retain the catheter tip at the desired location in the heart or other body tissue during the treatment or diagnosis.